Late Lunch Talk: Individual heterogeneity and early life conditions shape growth in a freshwater top-predator
Late Lunch Talk by Chloé Nater, CEES, University of Oslo
Individual heterogeneity and early life conditions shape growth in a freshwater top-predator
Growth is a central process in ecological and evolutionary dynamics and result of a complex interplay between life history schedules, individual heterogeneity, and environmental influences. We formulated a Bayesian biphasic growth model able to account for all of these components, and fit it to a unique 30-year time series of individual length measurements inferred from scale year rings of wild brown trout. Our analysis revealed a gradual decrease in average juvenile growth, which has carried over to adult life and contributed to decreasing sizes observed at the population level. Commonly advocated environmental drivers of growth like temperature and water flow did not explain much of this trend in our system, and overall persistent among-individual variation dwarfed temporal variation in growth patterns. Further analysis of individual random effects also suggested higher mortality for individuals with fast growth and large growth capacity. We thus demonstrate how disentangling among-individual and among-year variation in non-linear growth models can explain long-term body size trends observed at the population level and provide preliminary insights into potential size-dependence of mortality.